Vehicles can be equipped with retractable windshield wiper installations such that the windshield wiper mechanism itself is parked inside a closed housing below the hood of the vehicle when not in use for windshield wiping purposes. When it is required for use, a deployment mechanism, operated by a motor, is activated so as to raise the windshield wiper out of the housing and to put the various components of the system into appropriate positions for wiping the windshield of the vehicle.
In designing such a system, it is in particular necessary to resolve the problem of folding up the wiper arm that supports the wiper blade, ready to be parked in the housing. The wiper blade is carried by a blade carrier which is pivoted to a blade carrier support arm, and the length of the wiper arm, that is to say the support arm and the blade carrier combined, is too large for it to be easily parked without the blade carrier having first been folded back against the support arm.
Hitherto, systems have been proposed in which the blade carrier, pivoted to the end of the blade carrier support arm, can be either folded back along the support arm or else deployed within the length of the support arm. A deployment motor, which is disposed on the blade carrier support arm and which is activated when deployment or folding back is required, enables the blade carrier to be moved from its folded back position to its deployed position and vice versa. When the windshield of the vehicle is to be wiped by the blade, the blade carrier is in the deployed position and a wiper motor drives the assembly of the support arm and blade carrier in oscillating movement, first in one direction and then in the other.
Thus, the wiper motor has to drive in rotational movement an assembly the inertia of which is substantially greater than with conventional, non-retractable, windshield wipers, due to the numerous additional members necessitated by the mechanism for deployment and folding back. But as in any oscillating system, in which it is necessary periodically to reverse the direction of rotation of the assembly, the inertia of the assembly to be driven is a most important factor to be taken into account.